The present invention relates to a telescopic stay or brace assembly for supporting two objects which are capable of being folded relative to one another, and particularly, although not exclusively, for supporting a work surface which can be folded relative to a frame structure.
In the case of foldable work surfaces which are supported in their raised positions by means of some suitable form of brace assembly, it is desirable that the brace can be manipulated easily, both when locking the brace subsequent to raising the work surface and when releasing the brace in order to lower the work surface. The brace must also be capable of locking the raised work surface reliably and to form a firm support for the work surface in the desired working position thereof.
A telescopic brace or stay which fulfills these desiderata to a large extent is known from the British Patent Specification No. 1 524 281 and comprises two tubes which can be displaced telescopically in relation to one another and the mutually opposite ends of which are each pivotally connected to a respective one of said two objects, and further comprises an inner guide tube arranged within the telescopic tubes, a tension spring which extends axially through all tubes, and locking means for releasably locking the telescopic tubes in a given working position relative to one another.
This known brace, however, is encumbered, inter alia, with the following drawbacks. When the telescopic tubes are retracted one within the other, the inner guide tube projects beyond the ends of the telescopic tubes, therewith preventing the brace from being fitted directly to a complete surface, e.g. a wall. Instead it is necessary to fit the brace to a surface which is laterally offset, so that the inner guide tube can be permitted to project out from the telescopic tube. Alternatively, it may be necessary to form a hole in a rearwardly lying wall in order to accommodate the guide tube.
When braces of this particular kind are intended, inter alia, to support tables or work surfaces in trains, watercraft, caravans and in other cases where relative movement of the aforesaid two objects can occur, it is essential that the brace assembly is capable of preventing the work surface from swinging, or of damping such swinging movement, when the work surface is in its lowered position. Since, when the known brace assembly is retracted the aforesaid inner guide tube projects from the outer telescopic tube, the tension spring has no damping effect whatsoever on the swinging movement of the downwardly folded work surface.
Our earlier U.S. patent application No. 104,022 describes and illustrates a brace assembly of the aforesaid kind which, inter alia, eliminates these drawbacks. A characteristic feature of this improved brace assembly is that the inner guide tube is fixed axially in relation to one of the telescopically movable tubes and accompanies the movement of this one tube in relation to the other telescopic tube. A further characteristic feature is that each end of the tension spring is fixed relative to a respective telescopic tube and that the length of the spring is such that the spring will constantly exert on the tubes a force which strives to retract the tubes one inside the other.
The inner guide tube of this improved brace assembly will not protrude from the telescopic tubes, and positive damping of any relative movement between the objects to which the brace is fitted is effected by means of the spring, even when the tubes are retracted and the work surface is folded down.
A common drawback with both of these earlier known brace assemblies however, is that the telescopic tubes can be drawn out completely from one another. In the case of the aforesaid known brace assemblies in which the tubes fit closely one within the other and in which the tension spring extends axially through the tubes, it is difficult, without further complicating the construction and increasing its costs, to provide a stop which will prevent one tube from being withdrawn completely from the other.